2022 Volume 108 Issue 10 Pages 772-783
In this study, we investigated the strain-history dependence of ductile fracture behavior in ferrite–pearlite (FP) two-phase steels. The mechanism of this dependence was analyzed using finite element (FE) simulation. The orthogonal strain path changes were subjected to single-phase ferrite steel, two types of FP steels with different pearlite fraction, and single-phase pearlite steel. After the tensile pre-deformation, secondary tensile deformation was applied in the same direction or orthogonal to the first direction. The results showed that the elongation was higher when the secondary deformation was applied in the direction orthogonal to the pre-deformation, compared with that in the no-path change case. The elongation improvement due to the path change was greater with higher pre-deformation and pearlite fraction. The mechanism was investigated by analyzing the localization behavior of plastic deformation in the microstructure via FE simulation using a three-dimensional heterogeneous microstructure model. The simulations showed that the deformation path change in FP steel suppressed local accumulation of damage by changing the strain localization region owing to strength heterogeneity between the two phases.